1. Field of the Invention
The present invention relates to a cermet blade member which exhibits a superior thermoplastic deformation resistance and a high wear resistance under particularly severe conditions associated with high heat-generation. The present invention also pertains to a surface-coated cermet blade member having an excellent bonding strength between a cermet substrate and a hard coating layer.
2. Prior Art
Heretofore, there has been well known a blade member of titanium carbo-nitride (TiCN) based cermet for cutting steels, ductile cast irons and the like, comprising:
10% to 49% by weight of a binder phase including nickel (Ni) as a main ingredient and
the remainder of a hard dispersed phase composed of TiCN, as described in Japanese Patent Application First Publication No. 52- 94,814.
The conventional blade member of TiCN based cermet as described above has a relatively high proportion of the binder phase with respect to the hard dispersed phase. For this reason, the conventional blade member is vulnerable to thermoplastic deformation within a relatively short period of time, under particularly severe conditions in heavy duty cutting such as high feed cutting and deep cutting, or high-speed cutting accompanied with high heat generation at the cutting edge, these types of cutting being employed in the recent trend of energy-saving and high speed cutting processes.
In addition, as described in Japanese Patent Application First Publication No. 63-134,654, a surface-coated blade member for cutting steel, ductile cast iron and the like has been proposed which comprises a TiCN based cermet substrate and a hard coating layer deposited on the substrate, the hard coating layer having an average layer thickness of 0.5 .mu.m to 10 .mu.m. The hard coating layer has at least one layer, each layer being made of a titanium carbide, a titanium nitride, or a titanium carbo-nitride. The TiCN based cermet substrate has the following composition:
15% to 20% by weight of a binder phase including nickel (Ni) and cobalt (Co);
20% to 40% by weight of a hard dispersed phase of metal carbide; and
the remainder of a hard dispersed phase composed of TiCN and unavoidable impurities.
The conventional surface-coated blade member as described above does not have a sufficient bonding strength between the substrate and the coating layer. For this reason, under particularly severe conditions in heavy duty cutting or high-speed cutting, accompanying the recent trend of energy-saving and high-speed cutting processing, the hard coating layer of the surface-coated blade member is susceptible to separation from the substrate, terminating the tool life of the blade member within a relatively short period of time.